Medical leads with segmented electrodes and methods of fabrication thereof

ABSTRACT

In one embodiment, a neurostimulation lead comprises: a lead body comprising a plurality of conductor wires; and a molded stimulation tip end comprising a plurality of segmented electrodes, hypotubes, and an annular frame structure: wherein (i) each segmented electrode of the plurality of segmented electrodes has an inner surface, an outer surface, and step-down region embedded within polymer material of the molded stimulation tip end, (ii) each respective hypotube is directly welded to the inner surface of a corresponding segmented electrode of the plurality of segmented electrodes.

RELATED APPLICATION

This application is a division of U.S. patent application Ser. No.14/541,795, filed Nov. 14, 2014, which claims priority to U.S.Provisional Application Ser. No. 61/912,517, filed Dec. 5, 2013, whichis incorporated herein by reference.

TECHNICAL FIELD

This application is generally related to stimulation leads, and inparticular to stimulation leads with segmented electrodes and methods offabrication.

BACKGROUND INFORMATION

Deep brain stimulation (DBS) refers to the delivery of electrical pulsesinto one or several specific sites within the brain of a patient totreat various neurological disorders. For example, deep brainstimulation has been proposed as a clinical technique for treatment ofchronic pain, essential tremor, Parkinson's disease (PD), dystonia,epilepsy, depression, obsessive-compulsive disorder, and otherdisorders.

A deep brain stimulation procedure typically involves first obtainingpreoperative images of the patient's brain (e.g., using computertomography (CT) or magnetic resonance imaging (MRI)). Using thepreoperative images, the neurosurgeon can select a target region withinthe brain, an entry point on the patient's skull, and a desiredtrajectory between the entry point and the target region. In theoperating room, the patient is immobilized and the patient's actualphysical position is registered with a computer-controlled navigationsystem. The physician marks the entry point on the patient's skull anddrills a burr hole at that location. Stereotactic instrumentation andtrajectory guide devices are employed to control the trajectory andpositioning of a lead during the surgical procedure in coordination withthe navigation system.

Brain anatomy typically requires precise targeting of tissue forstimulation by deep brain stimulation systems. For example, deep brainstimulation for Parkinson's disease commonly targets tissue within orclose to the subthalamic nucleus (STN). The STN is a relatively smallstructure with diverse functions. Stimulation of undesired portions ofthe STN or immediately surrounding tissue can result in undesired sideeffects. Mood and behavior dysregulation and other psychiatric effectshave been reported from stimulation of the STN in Parkinson's patients.

To avoid undesired side effects in deep brain stimulation, neurologistsoften attempt to identify a particular electrode for stimulation thatonly stimulates the neural tissue associated with the symptoms of theunderlying disorder while avoiding use of electrodes that stimulateother tissue. Also, neurologists may attempt to control the pulseamplitude, pulse width, and pulse frequency to limit the stimulationfield to the desired tissue while avoiding other tissue.

As an improvement over conventional deep brain stimulation leads, leadswith segmented electrodes have been proposed. Conventional deep brainstimulation leads include electrodes that fully circumscribe the leadbody. Leads with segmented electrodes include electrodes on the leadbody that only span a limited angular range of the lead body. The term“segmented electrode” is distinguishable from the term “ring electrode.”As used herein, the term “segmented electrode” refers to an electrode ofa group of electrodes that are positioned at approximately the samelongitudinal location along the longitudinal axis of a lead and that areangularly positioned about the longitudinal axis so they do not overlapand are electrically isolated from one another. For example, at a givenposition longitudinally along the lead body, three electrodes can beprovided with each electrode covering respective segments of less than120° about the outer diameter of the lead body. By selecting betweensuch electrodes, the electrical field generated by stimulation pulsescan be more precisely controlled and, hence, stimulation of undesiredtissue can be more easily avoided.

Implementation of segmented electrodes are difficult due to the size ofdeep brain stimulation leads. Specifically, the outer diameter of deepbrain stimulation leads can be approximately 0.06 inches or less.Fabricating electrodes to occupy a fraction of the outside diameter ofthe lead body and securing the electrodes to the lead body can be quitechallenging.

SUMMARY

In some embodiments, a method for fabricating a neurostimulationstimulation lead comprises: providing a plurality of ring components andhypotubes in a mold; molding the plurality of ring components and thehypotubes to form a stimulation tip component for the stimulation lead;and forming segmented electrodes from the ring components afterperforming the molding. The hypotubes may be welded to the electrodesbefore placement within a mold for an injection molding process.According to any of the discussed embodiments, the method furthercomprises applying a first weld and a second weld to attach eachhypotube to a corresponding ring component. The molding process fillsthe interstitial spaces with suitable insulative material.

According to any of the discussed embodiments, the neurostimulation leadis adapted for long term implant within a patient. In one embodiment,the neurostimulation lead is a deep brain stimulation lead. Theneurostimulation lead may comprise a suitable configuration of segmentedelectrodes (four rows of two segmented electrodes, two rows of foursegmented electrodes, or two rows of three segmented electrodes with twoconventional ring electrodes as example configurations). According toany of the discussed embodiments, the neurostimulation lead may comprisea non-symmetric hour-glass radial marker.

According to any of the discussed embodiments, the method furthercomprises: providing a pre-molded frame component with multiple lumensabout the plurality of hypotubes, wherein the frame is placed about theplurality of hypotubes before the molding process is performed to retainthe plurality of hypotubes at respective angular positions during themolding process. The re-molding frame structure is integrated within thestimulation tip component by the molding process. The pre-molded framemay be fabricated using a suitable biocompatible polymer material.According to any of the discussed embodiments, the stimulation tipcomponents may employ a relatively stiff polymer material (e.g., shore75D) while polymer material of the lead body is relatively less stiff(e.g., shore 55D).

According to any of the discussed embodiments, the plurality ofhypotubes comprise different lengths for multiples ones or all of theplurality of hypotubes. The hypotubes extend from the molded portion ofthe stimulation or terminal tip by respective lengths. The differentlengths facilitate subsequent connection of the hypotubes to conductorwires of a lead body in a correct order.

According to any of the discussed embodiments, an insulative coating isdisposed on each hypotube of the plurality of hypotubes. The insulativecoating may be a parylene material (one or more respective polyxylylenepolymers). Weld operations may be performed on the coated hypotubes tomechanically and electrically connect the hypotubes to various othercomponents of the neurostimulation lead. For example, the conductorwires of a lead body of the neurostimulation lead may be welded to thecoated hypotubes.

According to any of the discussed embodiments, the method furthercomprises providing insulative material over an exposed portion of theplurality hypotubes after connection to conductor wires of a lead bodyand reflowing the insulative material to enclose the previously exposedportion of the plurality of hypotubes and to integrate a stimulationand/or connector tip component with the lead body. The insulativematerial may be provided in a “clam-shell” form to facilitate wrappingaround the connection region between the stimulation or terminal tip andthe lead body. The insulative material may be a suitable reflowablepolymer material.

According to any of the discussed embodiments, each ring component maycomprise a step-down region. The step-down region is secured underneaththe surface of the neurostimulation lead formed by the insulativematerial provided during the molding process. The roughness of thesurface of step-down region may be increased by bead-blasting tofacilitate bonding or adhesion to the insulative material providedduring the molding process. Also, the inner surface of the ringcomponents may be similarly processed to facilitate adhesion to theinsulative material provided during the molding process.

According to any of the discussed embodiments, the hypotubes areconnected to wires of a lead body of the neurostimulation lead. Themethod further comprises twisting the lead body from a firstconfiguration with linearly arranged conductor wires to obtain a secondconfiguration with helically arranged conductor wires. The methodfurther comprises heating the lead body to retain the helicalarrangement of conductor wires in the finished neurostimulation lead.The twisting may be performed before or after connection to thehypotubes.

In some embodiments, a neurostimulation lead is fabricated using any ofthe methods discussed herein. In some embodiments, a neurostimulationsystem includes an implantable pulse generator (IPG) and one or moreneurostimulation leads fabricated using any of the methods discussedherein.

The foregoing and other aspects, features, details, utilities andadvantages of the present disclosure will be apparent from reading thefollowing description and claims, and from reviewing the accompanyingdrawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIGS. 1A and 1B depict a stimulation tip component shown in respectiveviews according to some representative embodiments.

FIGS. 2A and 2B depict a terminal end component according to respectiveviews according to some representative embodiments.

FIGS. 3A-3C depict a lead body component according to somerepresentative embodiments.

FIGS. 4A-4F depict respective components of a stimulation tip componentaccording to some representative embodiments.

FIG. 5 depicts an additional view of a terminal end component accordingto some representative embodiments.

FIG. 6 depicts integration of a stimulation tip component with a leadbody component according to some representative embodiments.

FIG. 7 depicts a finished stimulation lead within a neurostimulation orother active medical device system according to some embodiments.

FIG. 8 depicts a flowchart of operations for fabrication of astimulation end component according to one representative embodiment.

FIG. 9 depicts a flowchart for operations for joining a stimulation endcomponent to a lead body component according to one representativeembodiment.

FIG. 10 depicts a plurality of different marker designs that permit theorientation of a stimulation lead with segmented electrodes to bedetermined post-implant.

FIG. 11 depicts the orientation of a lead with segmented electrodes andan orientation marker according to one representative embodiment matchedagainst corresponding images of the lead.

FIG. 12 depicts further images of segmented leads with markers accordingto some representative embodiments.

DETAILED DESCRIPTION

The present application is generally related to a process forfabricating a stimulation lead comprising multiple segmented electrodes.In one preferred embodiment, the lead is adapted for deep brainstimulation (DBS). In other embodiments, the lead may be employed forany suitable therapy including spinal cord stimulation (SCS), peripheralnerve stimulation, peripheral nerve field stimulation, dorsal root ordorsal root ganglion stimulation, cortical stimulation, cardiactherapies, ablation therapies, etc.

In some representative embodiments, multiple components are fabricatedand assembled to form a stimulation lead including segmented electrodes.Referring to FIGS. 1A and 1B, stimulation end component 100 is shown inrespective views. In one embodiment, stimulation end component 100 isfabricated by molding the respective components using a suitablebiocompatible polymer to form an integrated assembly. In one embodiment,injection molding is the process selected for fabrication of stimulationend component 100, although any suitable molding technique may beemployed. The various components include a plurality of electrodes andhypotubes. The electrodes are connected to a plurality of hypotubes. Thestimulation end component 100 may also include a radio-opaque marker topermit the orientation of the lead to be determined post-implant usingsuitable medical imaging. Stimulation end component 100 preferablyincludes a plurality of segmented electrodes. In one embodiment, adistal ring electrode, two rows of three segmented electrodes, and aproximal ring electrode are provided, although any suitable electrodeconfiguration may be selected. One other possible electrodeconfiguration includes two rows of four segmented electrodes. Anotherpossible electrode configuration includes four rows of two segmentedelectrodes.

FIGS. 2A and 2B depict terminal end 200 according to respective views.Terminal end component 200 may be fabricated in a substantially similarmanner to stimulation end component 100 using suitable moldingtechniques. Terminal end component 200 may preferably comprise ringcontacts for placement within the header of an implantable pulsegenerator (IPG). Terminal end component 200 may also comprise anon-active contact ring for use with a set screw and/or contact with aninitial seal element within the header of the IPG. Terminal endcomponent 200 preferably comprises a stylet guide and central lumen forthe stylet.

FIGS. 3A and 3B depict lead body component 300. In one embodiment, amulti-lumen component of insulative material is initially molded orotherwise suitably fabricated. Conductors are placed within the variouslumens as shown in FIGS. 3A and 3B. The conductors may extend from thedistal and proximal ends of the body of insulative material. A centrallumen is also provided in lead body component 300 for use of thefinished stimulation lead with a stylet. In some embodiments, afterplacement of the conductor wires, lead body component 300 is twisted oneor more times and subjected to heating (as shown in FIG. 3C). By heatsetting a twist configuration to the lead body component 300, transferof bending at one end of lead body component 300 to the other end oflead body component 300 is prevented. Preventing bend and otherdeformation transfers from occurring may be helpful during handling ofthe finished lead during an implant procedure.

FIGS. 4A-4D depict components of stimulation end component 100 accordingto some embodiments. In FIG. 4D, ring component 450 is shown. Ringcomponent 450 is a substantially annular structure of suitableconductive material. Ring component 450 includes one or more step-downregions 451 where the outer diameter is reduced. The step-down regionsmay permit ring component 450 to be more securely integrated within thebody of the stimulation end component 100 in the molding process. Thatis, the step-down regions 451 may be disposed below the outer surface ofthe insulative material after molding occurs. Also, step-down regions450 may be bead blasted to increase the roughness of the surface of theelectrodes to improve bonding or adhesion to the insulative material.Also, the inner diameter (not shown) of ring component 450 may besimilar processed. Other techniques for application of abrasivematerials to roughen the respective surfaces may be alternativelyapplied. The increase in surface roughness may further secure theintegration of the metal components with the insulative materialprovided during the molding process. Additionally, ring component 450may comprise longitudinal grooves or cuts (shown in FIG. 4F) along theinner diameter of component 450 to facilitate separation of thecomponent 450 into multiple segmented electrodes by a grinding processor other suitable processing. The reduced wall thickness along suchgrooves permits separation during grinding operations as detailed inU.S. patent Ser. No. 12/873,838, filed Sep. 1, 2010 (published as U.S.Patent Pub. No. 2011/0047795) which is incorporated herein by reference.

FIG. 4A depicts component 410 which includes the ring components 450(before grinding operations), ring electrodes, and the hypotubesintegrated using molded insulative material. Component 410 is subjectedto suitable grinding operations to provide stimulation tip component 420in which the grinding produces the segmented electrodes from ringcomponents 450. Pre-molded frame 425 (shown individually in FIG. 4C) isplaced over a portion of the hypotubes as shown in FIG. 4E to formstimulation end component 100. Frame 425 may provide stability tohypotubes within the interior of the finished stimulation lead andprevent hypotubes from migrating to the outer surface of the stimulationlead. Also, frame 425 may ensure that hypotubes are maintained in aregular angular pattern to facilitate connection with other portions ofthe stimulation lead. A portion of hypotubes may preferably remainexposed to facilitate subsequent lead fabrication operations. Also, thelengths of the hypotubes may be preferably staggered as shown in FIG.4E. The difference in length of the respective hypotubes permits readyidentification of the connection of a specific hypotube to acorresponding electrode to facilitate further integration operations forfabrication of the stimulation lead.

FIG. 5 depicts an additional view of terminal end component 500. Asdiscussed previously, terminal end component 500 may be fabricated insubstantially the same manner as stimulation end component 100. Terminalend component 500 may include a hypotube configuration (i.e., variedlengths of hypotubes) that mirrors the arrangement of hypotubes onstimulation end component 100 to facilitate the lead fabricationprocess. Terminal end component 500 may include a suitable framecomponent surrounding the hypotubes. Further, terminal end component 500may include an additional contact which is not connected to a hypotube.The additional contact may be employed for use with a set-screw in theheader of an extension and/or IPG.

FIG. 6 depicts integration of stimulation end component 100 with leadbody component 300. Lead body component 300 is placed next to “gear”component 650. Gear component 650 may be fabricated from suitablebiocompatible material such as PEEK or ETFE. Gear component 500comprises a plurality of grooves or channels for the conductors of leadbody component 300 and the hypotubes of stimulation end component 100.The conductors of lead body component 300 are placed within thehypotubes and suitable welding operations are performed (e.g., laserwelding). Clamshell component 610 is preferably placed over the exposedconnection region of conductors and hypotubes. Clamshell component 610is preferably fabricated from a reflowable (e.g., a biocompatiblepolyurethane or thermoplastic polycarbonate urethane) insulativematerial. The material of component 610 is selected to possess a lowerflow temperature than of gear component 650. When reflow operationsoccur, gear component 650 retains the hypotubes and/or conductors inplace and prevents mutual contact between such conductive material.Thereby, shorting between such components is prevented.

Similar operations may occur to connect the other end of lead bodycomponent 300 to terminal end component 200 to form the stimulationlead.

FIG. 7 depicts a finished stimulation lead within a neurostimulation orother active medical device system according to some embodiments.Neurostimulation system 700 includes pulse generator 720 and one or morestimulation leads 701. Examples of commercially available pulsegenerator include the EON™, EON MINI™, LIBRA™, and BRIO™ pulsegenerators available from St. Jude Medical, Inc. Other active medicaldevices could be employed such as pacemakers, implantable cardioverterdefibrillator, gastric stimulators, functional motor stimulators, etc.Pulse generator 720 is typically implemented using a metallic housingthat encloses circuitry for generating the electrical pulses forapplication to neural tissue of the patient. Control circuitry,communication circuitry, and a rechargeable battery (not shown) are alsotypically included within pulse generator 720. Pulse generator 720 isusually implanted within a subcutaneous pocket created under the skin bya physician.

As fabricated according to techniques described herein, lead 701 iselectrically coupled to the circuitry within pulse generator 720 usingheader 710. Lead 701 includes terminals (not shown) that are adapted toelectrically connect with electrical connectors (e.g., “Bal-Seal”connectors which are commercially available and widely known) disposedwithin header 710. The terminals are electrically coupled to conductors(not shown) within the lead body of lead 701. The conductors conductpulses from the proximal end to the distal end of lead 701. Theconductors are also electrically coupled to electrodes 705 to apply thepulses to tissue of the patient. Lead 701 can be utilized for anysuitable stimulation therapy. For example, the distal end of lead 701may be implanted within a deep brain location or a cortical location forstimulation of brain tissue. The distal end of lead 701 may be implantedin a subcutaneous location for stimulation of a peripheral nerve orperipheral nerve fibers. Alternatively, the distal end of lead 701positioned within the epidural space of a patient. Although someembodiments are adapted for stimulation of neural tissue of the patient,other embodiments may stimulate any suitable tissue of a patient (suchas cardiac tissue). An “extension” lead (not shown) may be utilized asan intermediate connector if deemed appropriate by the physician.

Electrodes 705 include multiple segmented electrodes. The use ofsegmented electrodes permits the clinician to more precisely control theelectrical field generated by the stimulation pulses and, hence, to moreprecisely control the stimulation effect in surrounding tissue.Electrodes 705 may also include one or more ring electrodes and/or a tipelectrode. Any of the electrode assemblies and segmented electrodesdiscussed herein can be used for the fabrication of electrodes 705.Electrodes 705 may be utilized to electrically stimulate any suitabletissue within the body including, but not limited to, brain tissue,tissue of the spinal cord, peripheral nerves or peripheral nerve fibers,digestive tissue, cardiac tissue, etc. Electrodes 705 may also beadditionally or alternatively utilized to sense electrical potentials inany suitable tissue within a patient's body.

Pulse generator 720 preferably wirelessly communicates with programmerdevice 750. Programmer device 750 enables a clinician to control thepulse generating operations of pulse generator 720. The clinician canselect electrode combinations, pulse amplitude, pulse width, frequencyparameters, and/or the like using the user interface of programmerdevice 760. The parameters can be defined in terms of “stim sets,”“stimulation programs,” (which are known in the art) or any othersuitable format. Programmer device 750 responds by communicating theparameters to pulse generator 720 and pulse generator 720 modifies itsoperations to generate stimulation pulses according to the communicatedparameters.

FIG. 8 depicts a flowchart of operations for fabrication of astimulation end component according to one representative embodiment. In801, pre-cut hypotubes are welded to electrodes that include singulation(e.g., grooves) and retention features (step-down regions). In someembodiments, the hypotubes are coated with insulative material beforebeing welded to the electrodes. In one embodiment, a suitable thin coat(e.g., approximately 12 μm) of parylene is provided over each hypotubeand the coated hypotubes are welded to the electrodes. The thin coatingof parylene permits electrical isolation to be maintained between thevarious conductive components. The thin coating of parylene preventsshorting between respective hypotubes and other electrically conductivecomponents. Further, it is has been determined by the present inventorsthat the thin coating of parylene does not affect the integrity of thesubsequently created weld points between the hypotubes and otherconductive components. In certain embodiments, the rings/electrodecomponents may be additionally or alternatively coated with a thin layerof insulative material (e.g., parylene).

In some embodiments, multiple weld operations are provided for eachhypotube. In one embodiment, a first weld is provided for each hypotubeat the proximal end of its ring component and a second weld is providedfor each hypotube at the distal end of its ring component. The first andsecond welds may improve the integrity of the connection between thehypotubes and the ring components. Pushing and pulling of the hypotubesmay occur by the injection of insulative material during the moldingprocess. This arrangement may cause the forces applied by the injectionprocess to be placed on the first weld while maintaining the mechanicaland electrical integrity of the second weld.

In 802, operations to load and shrink insulation onto hypotubes areperformed. In 803, hypotubes are loaded into pre-molded frame component.The frame component may comprise an annular structure with multiplelumens to accommodate each hypotube. In 804, the subassembly and markerare loaded into a suitable mold and injection molding operations areperformed to provide BIONATE™ or other suitable insulative materialunder the electrodes. After molding, the assembly is subjected togrinding to obtain the intended outer diameter size (805). In 806,annealing occurs. The terminal end component may be fabricated in asubstantially similar manner.

FIG. 9 depicts a flowchart for operations for joining a stimulation endcomponent to a lead body component according to one representativeembodiment. In 901, conductor cable ends are ablated to exposeconductive material from insulative sheaths about the conductors. In oneembodiment, one or more of the conductors are coated with a suitable dyematerial or other colorant to facilitate identification of a specificchannel in the finished stimulation tip component). In 902, the cablesare strung through lumens of a lead body. In 903, a PEEK or otherextrusion or molded component (see e.g., component 650 in FIG. 6) isinserted between the hypotubes to hold the hypotubes in place. In 904,cables are inserted into the hypotubes and laser welded, in 905, a“clamshell” of BIONATE™ (thermoplastic polycarbonate urethane) materialor other reflowable insulative material is loaded over the joint betweenthe components and reflow operations are performed. The reflowoperations may include providing a FEP shrink wrap and applyingsufficient heat as is known in the art of lead fabrication. The terminalend component may be joined to the lead body component in asubstantially similar manner.

FIG. 10 depicts a plurality of different marker designs that permit theorientation of a stimulation lead with segmented electrodes to bedetermined post-implant. One marker may be provided at a distal or tipof the stimulation lead. Additionally or alternatively, another markermay be provided proximal to the electrodes of the stimulation lead aboutthe outer surface of the lead body. FIG. 11 depicts the orientation of alead with segmented electrodes and an orientation marker according toone representative embodiment matched against corresponding images ofthe lead. FIG. 12 depicts further images of segmented leads with markersaccording to some representative embodiments.

Although certain embodiments of this disclosure have been describedabove with a certain degree of particularity, those skilled in the artcould make numerous alterations to the disclosed embodiments withoutdeparting from the spirit or scope of this disclosure. All directionalreferences (e.g., upper, lower, upward, downward, left, right, leftward,rightward, top, bottom, above, below, vertical, horizontal, clockwise,and counterclockwise) are only used for identification purposes to aidthe reader's understanding of the present disclosure, and do not createlimitations, particularly as to the position, orientation, or use of thedisclosure. Joinder references (e.g., attached, coupled, connected, andthe like) are to be construed broadly and may include intermediatemembers between a connection of elements and relative movement betweenelements. As such, joinder references do not necessarily infer that twoelements are directly connected and in fixed relation to each other. Itis intended that all matter contained in the above description or shownin the accompanying drawings shall be interpreted as illustrative onlyand not limiting. Changes in detail or structure may be made withoutdeparting from the spirit of the disclosure as defined in the appendedclaims.

When introducing elements of the present disclosure or the preferredembodiment(s) thereof, the articles “a”, “an”, “the”, and “said” areintended to mean that there are one or more of the elements. The terms“comprising”, “including”, and “having” are intended to be inclusive andmean that there may be additional elements other than the listedelements.

As various changes could be made in the above constructions withoutdeparting from the scope of the disclosure, it is intended that allmatter contained in the above description or shown in the accompanyingdrawings shall be interpreted as illustrative and not in a limitingsense.

The invention claimed is:
 1. A neurostimulation lead for implant withina body of a patient for stimulation of neural tissue of the patient, theneurostimulation lead comprising: a lead body comprising a plurality ofconductor wires; and a molded stimulation tip end comprising a pluralityof segmented electrodes, hypotubes, and an annular frame structure;wherein (i) each segmented electrode of the plurality of segmentedelectrodes has an inner surface, an outer surface, and step-down regionembedded within polymer material of the molded stimulation tip end, (ii)each respective hypotube is directly welded to the inner surface of acorresponding segmented electrode of the plurality of segmentedelectrodes, (iii) the annular frame structure comprises a plurality oflumens with respective hypotubes disposed within corresponding lumens,and (iv) the hypotubes are connected to respective ones of the pluralityof conductor wires of the lead body, wherein the plurality of hypotubesextend proximally from the stimulation tip end such that a proximal endof each respective hypotube exhibits a different distance from a singleproximal ring electrode disposed on the molded stimulation tip in aposition proximal to the plurality of segmented electrodes.
 2. Theneurostimulation lead of claim 1 wherein the plurality of conductorwires are disposed in a helical configuration within the lead body. 3.The neurostimulation lead of claim 1 wherein the plurality of hypotubesand an inner diameter of each electrode are coated with one or morerespective polyxylylene polymers.
 4. A neurostimulation system,comprising: an implantable pulse generator for generating electricalpulses to application to tissue of a patient; a neurostimulation leadfor implant within a body of a patient for stimulation of neural tissueof the patient, the neurostimulation lead comprising: a lead bodycomprising a plurality of conductor wires; and a molded stimulation tipend comprising a plurality of segmented electrodes, hypotubes, and anannular frame structure: wherein (i) each segmented electrode of theplurality of segmented electrodes has an inner surface, an outersurface, and step-down region embedded within polymer material of themolded stimulation tip end, (ii) each respective hypotube is directlywelded to the inner surface of a corresponding segmented electrode ofthe plurality of segmented electrodes, wherein the plurality ofhypotubes extend proximally from the stimulation tip end such that aproximal end of each respective hypotube exhibits a different distancefrom a single proximal ring electrode disposed on the molded stimulationtip in a position proximal to the plurality of segmented electrodes,(iii) the annular frame structure comprises a plurality of lumens withrespective hypotubes disposed within corresponding lumens, and (iv) thehypotubes are connected to respective ones of the plurality of conductorwires of the lead body.
 5. The neurostimulation system of claim 4wherein the plurality of conductor wires are disposed in a helicalconfiguration within the lead body.
 6. The neurostimulation system ofclaim 4 wherein the neurostimulation lead comprises a non-symmetrichour-glass radial marker.